Tidy up HardwareProperties literals in unit tests

Specifically:

* Use field names in the initializers themselves, rather than comments
  labelling each value
  * This reduces the chance of a value getting put in the wrong field by
    mistake, and allows us to omit values for the points below
* Remove initialization of deprecated screen_x_dpi and screen_y_dpi
  fields, except in the activity log tests (where we still want to check
  they're recorded correctly)
* Add default values of 0 for the left and top fields, which allows them
  to be omitted in most of the literals
* Add a common constant in the metrics interpreter tests, since they all
  use the same values and they're not referenced in assertions etc.

BUG=b:245989146
TEST=run unit tests

Change-Id: Ic1f09aa9f08db914eeb3fdbbbec72ef9f2b90f48
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/gestures/+/4874371
Commit-Queue: Harry Cutts <hcutts@chromium.org>
Tested-by: Harry Cutts <hcutts@chromium.org>
Reviewed-by: Denis Brockus <dbrockus@chromium.org>
Code-Coverage: Zoss <zoss-cl-coverage@prod.google.com>
23 files changed